Plot

SpongeBob and Patrick are given the task of pet sitting Sandy's pets when she is out of town. One of Sandy's pets is a small caterpillar named Wormy. Spongebob and Pat quickly befriend the caterpillar and they enjoy a day of play together, however; their fun is disrupted ; overnight, when Spongebob and Patrick are not at the Treedome, Wormy goes through quick metamorphosis and becomes a butterfly. When they come back in the morning, Patrick and Spongebob think the butterfly is a monster that ate Wormy. They go berserk as they try to trap the "monster", which manages to escape the Treedome while flying inside a bubble. Spongebob and Patrick begin to spread news of the terrible "monster" throughout Bikini Bottom. Mass chaos erupts and the whole town becomes destroyed and deserted.

Eventually, Sandy arrives at the shattered town in a few days. She immediately finds wormy and places him inside a jar. All the townsfolk cheer and celebrate the capturing of the butterfly "monster".

Home video releases

VHS

SpongeBob SquarePants: Sponge Buddies

DVD

SpongeBob SquarePants: Nautical Nonsense and Sponge Buddies

SpongeBob SquarePants: The Complete 2nd Season

SpongeBob SquarePants: The First 100 Episodes

Blu-ray

SpongeBob SquarePants: It's a SpongeBob Christmas!

Notes

The close up of the butterfly is really the head of a buzzing horse-fly.

When Patrick is with the people holding up SpongeBob and Sandy, he does not have his eyebrows. In another shot during the same scene, he does not have eyes.

In this episode while the bird is singing, apparently it's voice is the same to a European Robin in 2001 documentary nature film Winged Migration.

When SpongeBob and Patrick first discover Wormy as a butterfly, they both run in different directions, but end up at the same table in the middle of Sandy's treedome.

The bubble that SpongeBob blows to catch the butterfly is impossible to make because he has his helmet filled with water on.

When Sandy catches Wormy in a jar, the jar does not fill with water.

The warning poster SpongeBob and Patrick put up depict a Viceroy butterfly, while Wormy is actually a Monarch butterfly. Viceroys belong to a different family group of butterflies, and are smaller and less common than the Monarchs. The reason why Viceroys resemble Monarchs is due to Müllerian mimicry, in which two separate species that share a certain predatory defense mechanism (in this case, being nasty-tasting to birds) also share very similar warning patterns.

This was the first episode to feature Patrick's new design, featuring thicker eyebrows, instead of the usual "Z" eyebrows.

When Mr. Krabs and Squidward run away from Wormy, two pairs of underwear can be seen, but Squidward does not wear pants or underwear.

When Patrick is warning the other fish about the butterfly, his mouth does not sync up with the audio.

In the part of the episode where it shows people running away, there is one yellow fish flying.

When SpongeBob is saying "We did it, Patrick!" during the destruction scene, a meteor can be seen flying down until it falls offscreen in the background a few seconds later, a flash can be seen in the background, referencing the landing explosion.

There is a deleted scene about SpongeBob eating pie.

Some people recall the close up of the butterfly coming after Sandy says "I should get out of town more often".

At the beginning Patrick whistles, and SpongeBob says: "I didn't know you spoke bird!", and Patrick says "No, that's Italian". In the Italian version he says that it is Spanish.

The Krusty Krab cash register boat is drivable as seen in this episode.

When SpongeBob begs wormy not to eat him, his mouth didn't sync right.

When Patrick's helmet broke, acorns fell in it. The water should have been displaced and overflowed, but it stayed at the same level.

When SpongeBob and Patrick finally lead the butterfly outside, they only open the first door. There are two doors, so the butterfly should've stayed between the them, instead of making its way outside.

Nancy's dress changes from yellow to gray in one point where the Bikini Bottomites are being chased by Wormy as butterfly.

The mouse in the snake's digestive tract should be in the middle of the snake's body, not at the snake's tail.

Speaking of the snake, squirrels are much smaller than most snakes, so Sandy should have been dwarfed by her pet.*Snakes can eat squirrels, yet Sandy keeps one as a pet. In the same way, some people keep boas and pythons as pets, even though they're large enough to eat humans.

In the end when Sandy is coming back, a bus stop sign is shown. Usually Bus Stops are not green and triangle shaped.